1. Field of the Invention
This invention relates to an electronic component-recognizing device for taking an image of an electronic component lighted from below.
2. Prior Art
Conventionally, an electronic component-recognizing device of this kind has been disclosed e.g. in Japanese Laid-Open Patent Publication (Kokai) No. 6-61700. The electronic component-recognizing device includes a component-sensing camera for taking an image of an electronic component by utilizing reflected light from the electronic component, and a lighting mechanism for lighting from below the electronic component brought to a component-sensing station. The lighting mechanism is comprised of a light-emitting element formed to have an annular shape, a light guide for guiding light to the light-emitting element, and a lamp for launching light into the light guide. Illumination light emitted from the light-emitting element is reflected back from an electronic component, and the reflected light is taken into the component-sensing camera via an inner opening of the light-emitting element. The light-emitting element has an inner periphery thereof formed with a plurality of reflecting surfaces where exposed are output end faces of a large number of optical fibers forming the light guide from all radial directions, and which reflect output light from the optical fibers toward the electronic component at various angles. This permits an underside surface of the electronic component to be lighted from the various angles.
However, in the conventional electronic component-recognizing device, to illuminate an electronic component from the various angles, the inner periphery of the light-emitting element has the plurality of reflecting surfaces formed in a stepped manner or in tiers, which inevitably complicates the shape of the inner periphery, and hence machining of this portion of the device takes much time and labor, resulting in increased manufacturing costs of the device. Further, since the plurality of reflecting surfaces are formed in a stepped manner or in tiers as described above, the height of the whole light-emitting element is increased, and hence it is required to set an image-taking position at which an image of an electronic component is taken at a high location so as to prevent interference between the electronic component and the light-emitting element. As a result, the inner opening of the light-emitting element for taking in reflected light from the electronic component is also required to have an increased diameter, and at the same time, the distance between the output end of the light guide and the component-sensing camera is increased, which tends to attenuate the reflected illumination light and make the same nonuniform.
It is an object of the invention to provide an electronic component-recognizing device that is compact in size and simple in construction and enables an electronic component to be uniformly illuminated with light.
To attain the above object, the present invention provides an electronic component-recognizing device for taking an image of an electronic component brought to a component-sensing station, for recognition thereof, the electronic component-recognizing device including a component-sensing camera for taking the image of the electronic component by utilizing reflected light from the electronic component, and a lighting mechanism for lighting the electronic component.
The electronic component-recognizing device according to the invention is characterized in that the lighting mechanism comprises:
a light-diffusing radiator arranged annularly such that the light-diffusing radiator can diffuse illumination light and emit the diffused illumination light toward the electronic component obliquely from below;
a radiator holder for holding the light-diffusing radiator; and
a light source for supplying the illumination light to the light-diffusing radiator.
According to this electronic component-recognizing device, the lighting mechanism diffuses illumination light and emits the diffused illumination light toward an electronic component. Therefore, the electronic component-recognizing device is capable of irradiating the electronic component from many different angles without a plurality of reflecting surfaces formed in a stepped manner or in tiers. Further, since it is not required to form the plurality of reflecting surfaces in a stepped manner, it is possible to reduce the size of the light-diffusing radiator and simplify the shape of the same, thereby reducing machining cost of the device. Moreover, the reduction of the size of the light-diffusing radiator allows the height of the lighting mechanism to be reduced and an image-taking position for taking an image of the electronic component to be set at a lower location. As a result, an opening inward of the light-diffusing radiator, for taking in the reflected light can also be reduced in diameter. Additionally, the reduction of the size of the light-diffusing radiator makes it possible to shorten an optical path between the output end of the light source and respective portions of the light-diffusing radiator, thereby reducing attenuation of the illumination light to maintain uniform light radiation. In short, the electronic component-recognizing device according to the invention has a compact and simple construction that enables uniform lighting of an electronic component.
Preferably, the light-diffusing radiator is formed as a unitary annular member, and has an light-emitting surface having a convex arcuate cross-sectional profile with at least one normal on the convex arcuate cross-sectional profile being directed toward the electronic component.
According to this preferred embodiment, the light-diffusing radiator has a light-emitting surface formed to have a convex arcuate cross-sectional profile and having one or more normals on the convex accurate cross-sectional profile directed toward the electronic component. Therefore, it is possible to diffuse illumination light supplied from the light source for irradiation and uniformly emit the diffused illumination light in a large area around each normal, and hence it is possible to carry out light radiation which is effective when an area to be uniformly lighted is large, e.g. in the case of taking an image of a relatively large electronic component from a close position.
Alternatively, the light-diffusing radiator is formed as a unitary annular member and has an light-emitting surface having a concave arcuate cross-sectional profile with at least one normal on the concave arcuate cross-sectional profile being directed toward the electronic component.
According to this preferred embodiment, the light-diffusing radiator has a light-emitting surface formed to have a concave arcuate cross-sectional profile with one or more normals on concave arcuate cross-sectional profile being directed toward the electronic component. Therefore, it is possible to diffuse illumination light supplied from the light source for irradiation and uniformly emit the diffused illumination light such that light beams converge in the vicinity of each normal. This makes it possible to carry out light radiation which is effective when an area to be uniformly lighted is small and high resolution is required, e.g. in the case of taking an image of a relatively small electronic component from a remote position.
Preferably, the light-diffusing radiator is formed of an acrylic resin.
According to this preferred embodiment, the acrylic resin is used as the material of the light-diffusing radiator. Therefore, it is possible to mass-produce light-diffusing radiators which are compact in size and uniform in shape, thereby contributing to improved uniformity of light radiation as well as further reduction of the size and manufacturing costs of the device. In addition, the use of the resin makes it easy to change the shape (in cross section) of a light-diffusing radiator. Therefore, it is also possible to form a light-diffusing radiator into a desired shape, to thereby change the area to be irradiated with light. In short, the use of the resin makes it possible to increase the freedom of shaping the light-diffusing radiator.
Preferably, the radiator holder is arranged radially outward of the light-diffusing radiator, and contains at least one optical fiber for supplying the illumination light to the light-diffusing radiator.
Preferably, the electronic component-recognizing device further includes a beam splitter arranged downward of the light-diffusing radiator, for guiding the reflected light from the electronic component toward the component-sensing camera.
More preferably, the electronic component-recognizing device further includes a light-emitting surface element arranged downward of the beam splitter such that an optical axis of the light-emitting surface element coincides with a center line of the electronic component, for irradiating the electronic component with illumination light.
The above and other objects, features, and advantages of the invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.